The first complete mitochondrial genome of the agricultural pest Micromelalopha sieversi (Staudinger, 1892) (Lepidoptera: Notodontidae)

Abstract Micromelalopha sieversi (Staudinger, 1892) is a significant pest of Poplar trees in China. In this study, we used high-throughput sequencing to sequence the whole mitochondrial genome of M. sieversi. The length of the genome was 15,373 base pairs. The nucleotide composition was 39.8%, 11.5%, 8.0%, and 40.7% for A, C, G, and T, respectively. We used the maximum-likelihood method to construct a molecular phylogenetic tree based on complete mitogenome sequences of 19 Noctuoidea species as ingroups and five Geometroidea species as outgroups. The results indicate that the genus Micromelalopha is closely related to the genus Clostera in family Notodontidae.


Introduction
Notodontidae is a family of Lepidopteran origin, distributed worldwide with more than 2800 described species, mostly occurring in tropical regions.Moths in this family are medium-sized and adults do not feed.The caterpillars are known for their bizarre appearances and are arboreal insects that cause defoliation of their hosts (Choi et al. 2020).In China, Micromelalopha sieversi Staudinger, 1892 (Lepidoptera: Notodontidae) is an important pest of Poplar trees (Populus spp., family Salicaceae).Commonly, M. sieversi occurs in 3-4 generations in northeast China, but in 5-7 generations in central and southern China.Extensive overlap was found between generations and females did not show significant circadian rhythm-related vocalization behaviors during the light phase but did so during the dark phase (Fan et al. 2015).After mating, females deposit their eggs on the Poplar leaves.The larvae have five instar stages, and the mature larvae pupate in the deciduous layer during winter (Chen et al. 2014), typically causing mesophyll injuries that result in balding of Poplar branches, weakening the host and curtailing growth (Fan et al. 2014;Guo, Liu, Wang, et al. 2019).However, for such a significant pest, most studies have mainly focused on discussing plant-lepidopteran interactions (Bertea et al. 2019;Guo, Liu, Zhang, et al. 2019;Hilker et al. 2023), describing the effects of oviposition behavior on host plants (Guo et al. 2020), and investigating components of sex pheromone (Liu et al. 2019), with little exploration of its phylogeny.The complete mitochondrial genome of this species has not been reported in NCBI and other databases.Therefore, in the current study, we sequenced and annotated for the first time the complete mitochondrial genome (mitogenome) of M. sieversi and constructed a molecular phylogenetic tree.This research expands our understanding of its mitogenome characteristics and helps infer the phylogenetic position of the genus Micromelalopha.

Materials
The specimens of M. sieversi (Figure 1) were collected by light trapping on 30 September 2022 at Hanshou National Vegetable Base (28.91 � N, 111.95 � E, Hanshou, Changde City, China) by Xuan Dai.Meanwhile, the specimens and the genomic DNA were deposited in the Insect Collection of Hunan Agricultural University (contact person: Guo-Hua Huang, email: ghhuang@hunau.edu.cn),Changsha City, Hunan Province, China under the voucher number HAUHL081471.

Results
The full mitogenome of M. sieversi (GenBank accession number: OQ354976) is 15,373 bp in size.The mitogenome has an AT-rich region along with 13 protein-coding genes (PCGs), 22 transfer RNA (tRNA) genes, and two ribosomal RNA (rRNA) genes.Among these, 15 genes are transcribed on the minority strand (N strand), and the remaining 22 genes are transcribed on the majority strand (J strand).The nucleotides consist of A, C, G, and T, accounting for 39.8%, 11.5%, 8.0%, and 40.7%, respectively.The AT nucleotide content is 80.5% (Figure 2).The nucleotide length among the genes is 227 bp, distributed among 18 pairs of adjacent genes, with lengths ranging from 2 to 53 bp.There are 35 bp overlapping nucleotides, scattered between 12 pairs of adjacent genes, with length ranging from 1 to 9 bp.The length of A þ T rich region between 12S rRNA and trnM is 373 bp.The molecular phylogenetic tree based on complete mitogenome sequences is given in Figure 3.The family Notodontidae has polyphyletic groups, with one clade being sister to the association of Nolidae þ (Erebidae þ Noctuidae) with very weak support (41%) and the other clade being sister to all other Noctuoidea with strong support (100%).The genus Micromelalopha was closely related to the genus Clostera in the family Notodontidae that was a clade strongly supported by the bootstrap value of 100%.

Discussion and conclusions
As the first report on the mitogenome of the genus Micromelalopha, its gene order and AT content are highly similar to other Notodontidae mitogenomes (Zhu et al. 2017(Zhu et al. , 2018)).Phylogenetic inference based on the 13 PCGs of this mitogenome shows a relatively clear positioning of the genus Micromelalopha within Notodontidae.Taken together, the mitogenome of M. sieversi could contribute to our understanding of mitogenome characteristics and help infer the phylogenetic position of the family Notodontidae.

Figure 1 .
Figure 1.Reference image of adult of Micromelalopha sieversi.(A) The dorsal view of M sieversi; (B) the ventral view of M. sieversi.These images from our specimen were taken by DX.

Figure 2 .
Figure 2. Mitogenome pattern map of Micromelalopha sieversi.Grey arrows indicate the direction of gene transcription.Genes inside the circle are coded in the majority strand (J-strand); genes outside the circle are coded in the minority strand (N-strand).